The railroad industry employs a large variety of freight railroad cars for transporting various different products. Each freight railroad car typically has hundreds, if not thousands, of different components. Certain of these freight railroad car components are considered to be railroad car high friction components because they are configured and positioned in the railroad car to engage under pressure a corresponding railroad car component of the railroad car while one or both of these components move relative to each other. For brevity, each railroad car high friction component is referred to herein as the high friction component, and the corresponding railroad car component is referred to herein as the corresponding component. For each high friction component and its corresponding component, when one or both of these engaging components move relative to one another, a certain amount of friction is created or exists between these engaging components. The friction between each high friction component and its corresponding component serves an important function in the control of the railroad car during movement of the railroad car along the tracks. One such important function is to provide appropriate damping characteristics to control ride quality of the railroad car.
Each high friction component and its corresponding component are preferably configured such that the amount of friction created between that high friction component and its corresponding component is at an optimal amount or within an optimal range. If the amount of friction is at the optimal amount or within the optimal range, these components best perform their intended functions. If the amount of friction between a high friction component and its corresponding component is slightly above the optimal amount or above the optimal range, or is slightly below the optimal amount or below the optimal range, these engaging components will typically operate, but will not optimally operate to provide their intended functions. Such non-optimal operation causes many problems such as, but not limited to: (a) excessive wear on these components; (b) excessive wear on other components of the railroad car; (c) excessive use of fuel which also creates excessive environmental pollution; (d) premature maintenance cycles; and (e) periodic lube cycles. If the amount of friction between a high friction component and its corresponding component is substantially above the optimal amount or above the optimal range, or is substantially below the optimal amount or below the optimal range, these components may not operate within maximum or minimal acceptable levels of providing their intended functions, or may not operate at all.
For each different high friction component, many different factors typically affect the amount of friction created between that high friction component and it corresponding component during operation of the railroad car. Certain of these factors also change over time as the railroad car is in service, as environment conditions change, and as these components and other components of the railroad car wear. It should thus be appreciated that it is very difficult for railroad car builders or railroad car component builders, for each high friction component, to have that high friction component operate at an optimal amount or with the optimal range.
While various different components of freight railroad cars are typically high friction components, the present disclosure uses friction wedges, constant contact side bearings, truck bolster center bowl liners, and brake beam extension heads as examples of such high friction components. It should however be appreciated that the problems with such high friction components discussed herein and the solutions to such problems discussed herein are not limited to such example components.
More specifically, previously known railroad car friction wedges provided metal to metal contact between the engagement face of the friction wedge and the corresponding engagement surface of the side frame column. This metal to metal contact produced very high (i.e., substantially above optimal) amounts of friction between these components and caused high rates of wear on their engaging surfaces. This metal to metal contact often created a slip stick effect that was hard to control and which often significantly varied with environmental changes (such as dramatic temperature swings or humidity changes). This metal to metal contact and the resulting problems made freight railroad car ride quality less controllable and failed to provide optimal operation of freight railroad car suspensions.
To solve these problems resulting from this undesired metal to metal contact between friction wedges and their corresponding side frame columns, certain friction wedges have been made with friction reducing pads bonded or otherwise attached to the entire or substantially the entire face of the friction wedge. Examples of these pads are disclosed in U.S. Pat. Nos. 6,691,625; 6,688,236; 6,701,850; 6,971,319; and 7,389,731. These friction reducing pads are placed between the engaging surfaces of the high friction component and the corresponding component, thereby separating these surfaces and preventing metal to metal contact between these components.
Known friction wedges with these pads have certain disadvantages. First, adding these pads to the friction wedges significantly increases the cost of the friction wedges. For example, for the friction wedges which include pads bonded to the engagement surface, the bonding process is relatively costly at least because it involves multiple manufacturing steps to effectuate the bond. Second, the bonded pads are prone to chipping and delaminating from the friction wedge engagement face. For example, failure of the material of the pad can occur from edge loading. Third, these pads are generally employed as sacrificial elements which are configured and manufactured to be worn out and replaced after certain periods of time or service. The need to regularly replace these worn, damaged, or destroyed pads increases the overall maintenance needed for freight railroad cars employing such friction wedges with these pads, and thus increases the overall cost of operating the freight railroad cars with such friction wedges. Fourth, the composite material of these pads is also more compressible than the respective metal engagement surfaces or faces of the friction wedges and corresponding components. Such compressibility of the material of the pad attached to the face of the friction wedge can sacrifice the ability of the friction wedge to hold the truck in a square position (which is sometimes called the warp damping/stiffness characteristic). Fifth, eliminating the metal to metal contact between these engaging components eliminates the advantages provided by such metal to metal contact, and particularly the overall strength and pressure tolerances of such metal, and particularly, such steel components. Accordingly, there is a need for railroad car friction wedges which overcome the above problems.
As mentioned above, another example high friction component with various disadvantages is a railroad car constant contact side bearing. Known constant contact side bearings generally create a higher truck torque that enables the truck to better handle curves in the tracks and high speed stability. Previously employed constant contact side bearings also provided metal to metal contact with the mating surfaces of the car underbody (or wear plate thereon) which produced high (i.e., substantially above optimal) amounts of friction between these engaging metal surfaces and caused high rates of wear on these engaging metal surfaces. Constant contact side bearings with sacrificial wear pads have also been also employed to reduce such undesired high amounts of friction between these metal surfaces. However, similar to friction wedges with these pads, constant contact side bearings with sacrificial wear pads are likewise more costly to manufacture, susceptible to chipping and delaminating, and eliminate the advantages provided by metal to metal engagement. Accordingly, there is also a need for constant contact side bearings which overcome these problems.
It should be appreciated from the above discussion of high friction components, such as friction wedges and constant contact side bearings, that there is an overall need for better railroad high friction components such as, but not limited to: (a) friction wedges; (b) constant contact side bearings; (c) bowl liners; (d) brake beam extension heads; (e) roller bearing adapters; (f) roller bearing adapter liners; and (g) side bearing vertical walls.